Submersible pumps like the kind used in oil fields are designed for downhole applications. They typically have a cylindrical shape with a diameter that allows them to be inserted within the casing of the well. The length of the pump can vary from 20 feet to 80 feet or more depending upon the amount of pressure and volume necessary for the application. These submersible pumps have the capability of pumping extremely large volumes of fluid in a very short time. Because of their ability to pump large volumes of fluid very rapidly, there are many surface applications for these submersible pumps. In order to use the pumps on the surface it is necessary to mount the pump horizontally on a skid. The pump can then be powered with a standard combustion engine or electric motor depending upon the utilities available at the application site.
In using the submersible pumps a great amount of thrust is generated by the force of the fluid flowing through the pump. Because of this force, it is necessary to have a thrust box between the pump and the electric motor. The drive shaft of the electric motor is coupled to the drive shaft of the thrust box. The opposite end of the thrust box drive shaft is coupled to the submersible pump. The thrust box is designed to absorb the thrust generated by the pump and transfer it back to the pump housing. This prevents the thrust generated by the pump from being absorbed by the combustion engine or electric motor driving pump. If the combustion engine or electric motor were coupled directly to the submersible pump this force would quickly destroy the bearings of the engine or motor.
There currently are many thrust boxes on the market, however, there are several shortcomings in their design. First, the thrust boxes on the market do not have a circulated and cooled lubricant. This creates problems with heat build up and lubricant failure which greatly shortens the life of the thrust box. Second, the thrust boxes rely upon seals which are held in place by clip rings mounted in grooves in the shaft. The groove cut in the shaft can introduce stress cracks in the shaft.
If the submersible pump, thrust chamber and motor are moved from one job site to another it often requires that the pump be operated at a different pressure. Because of the different pressure, different seals must be used to seal both the inlet end of the pump and the case of the thrust chamber. The various seals have different lengths. The distance between the grooves in the shaft and the case of the thrust box must vary to accommodate the length of the new seal. This in turn means that for different applications a different shaft must be used. This leads to a large number of different shafts which could possibly be used with a submersible pump and thrust box system. The operator or manufacturer must either stock these various shafts or have them custom made for each application. Because of the cost of maintaining inventory, most manufacturers custom make these shafts per the operator's specification. This creates increased down time and loss of operating revenue for the operator if they must change out the shaft and/or thrust box due to relocating the equipment or mechanical failure of the equipment.
A further draw back to the prior art horizontally mounted submersible pump systems is that the skid is manufactured such that the electric motor or pump must be removed from the skid in order to remove the thrust box. The thrust box is typically the component most likely to fail. When the electric motor or engine is removed from the skid it must be realigned along with the thrust box in order to reinstall the thrust box and motor. This too leads to increased down time and loss of operating revenue for the operator.